People always ask me where can I find this or that wallpaper.
When making tutorials variety is providing new wallpapers all the time.
I never go look for a wallpaper.
If there is a wallpaper I like, I will save it on my account at https://desktoppr.co/erikdubois.
As a result it will be saved on my dropbox that is linked to that website.
So if you see a wallpaper you like, see if I have saved it on desktoppr.
Another way to find the wallpaper in question, is using a reverse image search like
Upload the screenshot to this website and select the best possible resolution for your computer.
Extra tip:
In the video I use gimp to cut off the watermark in the wallpaper.
Other alternatives
https://www.duplichecker.com/reverse-image-search.php
https://images.google.com/ and upload the image there